A 22-year-old student has been jailed for 18 months after carrying out cyber attacks with hacking group Anonymous.

Christopher Weatherhead, of Holly Road, Northampton, was convicted last month for taking part in distributed denial of service, or DDoS, attacks on sites including Visa, Mastercard and PayPal.

The attacks on PayPal cost the company £3.5m.

They paralysed computer systems by flooding them with an intolerable number of online requests.

Victims' websites would be directed to a page displaying the message: "You've tried to bite the Anonymous hand. You angered the hive and now you are being stung."

Weatherhead was studying at Northampton University when he joined the cyber campaign.

He was sentenced at Southwark Crown Court along with Ashley Rhodes, 28, who was jailed for seven months after pleading guilty.

The pair were charged with conspiring to impair the operation of computers between August 1, 2010 and January 22, 2011.

Co-defendant Peter Gibson, 24, of Castletown Road, Hartlepool, was deemed to have played a lesser role in the conspiracy, which he also admitted, and given a six-month suspended sentence.

Jake Birchall, 18, from Chester, will be sentenced on February 1. He had also admitted the conspiracy.

Judge Peter Testar said: "It is intolerable that when an individual or a group disagrees with a particular entity's activities they should be free to curtail that activity by means of attacks such as those which took place in this case."

During Weatherhead's trial the court heard that PayPal was attacked repeatedly between December 8 and 17, 2010 after it decided not to process payments on behalf of the Wau Holland Foundation, an organisation involved in raising funds for WikiLeaks.

The websites that fell victim to the cyber attacks were chosen by Anonymous, as part of so-called Operation Payback, because the hackers did not agree with their views.